Neighbour finds toddler 'passed out in the street' after she swallowed parents' heroin.

Eighteen-month-old Alonna Bolden was found passed out on the pavement, blue in the face and struggling to breathe, not far from her home in the US state of Ohio.

Her parents, Brandy Estep and Jason Bolden, lay unconscious on the kitchen floor after taking heroin.

According to local TV station WSAZ, horrified neighbour Laura Royal found Alonna on the pavement outside, calling the police and rushing the little girl inside.

toddler heroin overdose
Little Alonna was found unconscious outside her home by a neighbour. Image via Facebook.

"When I actually looked back at the baby, she was blue," she said.

She said she rushed Alonna into her parents' apartment, when the little girl's father, 41-year-old Jason Bolden, allegedly woke and began frantically searching the home for heroin.

He reportedly told Royal he did not want to take the little girl to the hospital "for fear he might be jailed".

"He kept on saying it was her sugar...He knew," she said.

Police believe Alonna - who is now recovering in hospital in a serious but stable condition - suffered a heroin overdose after discovering her parent's drugs and swallowing them, although they are still awaiting test results to confirm what the toddler ingested.

toddler heroin overdose
Alonna's mother, Brandy Estep, was unconscious inside her home. Image via Facebook.

"It's heart-wrenching especially when you have kids of your own and you can relate to what's going on," Capt. Lynn Brewer of Portsmouth police said.

"At that age, everything goes into their mouths. They pick it up, they stick in in their mouth. I don’t care what it is. That’s why you have to be so careful about keeping an eye on your kids."

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Jason, along with Alonna's mother, 26-year-old Brandy Estep, have been charged with third-degree felony child endangerment following the incident. If convicted, they could face up to three years in prison.

The pair remain in police custody, and more charges may be filed against the couple.

toddler heroin overdose mother
Both of Alonna's parents have been charged over the incident. Image via Portsmouth Police Department.

Royal told WSAZ that on a sober day, Brandy was a great mother.

"On a clean, sober day, you couldn't ask for a better mother. But on getting high days, she's one of the worst," she said.

"And if she's going to continue to get high, she doesn't deserve her kids."